This invention relates generally to a power driven tool of the type having a nosepiece for holding an article such as a screw or nail having a head and a shank in alignment with a driver which drives the article against a workpiece. More particularly, the invention is concerned with an improved nosepiece for such tools. Selected for illustration of the invention is a hand held power screw driver.
Conventional tools of the type under consideration fall generally into two categories. In one, the screw to be driven is fed to the rear of a pair of jaws aligned with the driver and spring biased to closed condition. The point or front end of the screw is forced through the jaws until the head of the screw abuts against rear faces of the jaws. When the driver is advanced, it forces the screw forwardly causing the head to separate the jaws, thereby releasing the screw so that it can be driven against or into the work.
In this type of tool a succession of screws is usually fed to the jaws, one at a time, from a magazine or through a pneumatic tube, or the like. This type of tool is thus inherently relatively expensive and bulky and is unsuited for use in many operations where it is desired to load the screws into the tool by simply inserting them head first into the front of the nosepiece. Moreover, the jaws in the rear-loading nosepiece must be biased together with sufficient force to prevent the screw head from separating them and escaping during the jaw-loading procedure. The magnitude of this force renders it difficult and impracticable to try to load screws head first into the front end of the jaws. If the force were diminished sufficiently to facilitate easy front loading of the jaws, they would not hold a screw satisfactorily.
In the other conventional category, the screws are loaded head first into or onto the tool, but the holding device comprises simply a magnetized bit on the driving tool. The deficiencies of this arrangement are numerous and notorious: the bits are relatively expensive and must be replaced frequently since they will not hold a screw when even slightly worn; they will not hold a screw unless clear of dirt and metal particles and thus must be cleaned frequently; the bit will not hold the screw unless the screw head is rotationally aligned so that its slotting mates with the bit; the axis of the screw must be precisely aligned with that of the screw driver to avoid loosing the screw or grinding chips off of a screw head which then requires cleaning of the bit; the bit will not hold in horizontal position a relatively long shank screw having a small diameter head; in general, magnetic bits are only suitable for use with Phillips head screws and not straight slotted screws; under optimum conditions, a screw can be knocked off of the bit or cocked on the bit if even lightly brushed against or by another object.
A third conventional category of screw driver utilizes a magnetic bit in combination with a spring-type guide which engages the outer periphery of the screw head, but this arrangement is only useful where the screw is of a special type having a circumferential flat portion against which the guide engages to provide lateral support for the screw.
The object of the present invention is to provide a front loading nosepiece structure which is relatively simple and inexpensive, quick and convenient to use, and which is improved to eliminate the deficiencies of conventional front loading type screw drivers.
A feature of the nosepiece of the present invention is a ball-grip arrangement which enables a screw to be loaded into the tool through its front end in such manner that the head of the screw becomes firmly but releasably held and locked in position within the nosepiece with its shank projecting axially out of the front end of the tool.
This feature provides desirable advantages in that loading of a screw into the tool is simplified, and quickly obtained. The grip of the nosepiece upon the screw is firm so as to prevent the screw from cocking or dropping out during positioning of the screw relative to the work, or during the driving operation. The visibly projecting shank of the gripped screw enables the operator to accurately position the screw relative to the work.
Another advantageous feature of the nosepiece is a travel release structure associated with the ball-grip arrangement which cooperates with ball elements in the nosepiece during loading to obtain the positive grip of the nosepiece upon the screw, and which functions during the final stage of driving the screw to effect automatic release of the head of the screw from its gripped condition to permit it to be moved out of the nosepiece and finally seated in the work.
In accordance with the invention, there is provided a screw holding nosepiece for a screw driving tool having a screw driving bit, comprising inner and outer sleeve members having an axial slidable relation to one another, a coupling for supporting the sleeves to the housing of the tool for relative axial movement in coaxial relation to the driving bit of the tool, releasable blocking means carried by the inner sleeve normally blocking entry of the head of a screw into the inner sleeve, means carried by the outer sleeve having response to a predetermined relative retraction of the inner sleeve to effect release of the blocking means from its blocking condition so as to allow entry of the head of a screw into the inner sleeve beyond the blocking means, and spring means having response to said retracted relation of the inner sleeve to return the inner sleeve and the blocking means to their normal position so as to block the head of a screw previously entered into the inner sleeve beyond the blocking means from escaping out of the inner sleeve.